Data Storage System

ABSTRACT

The present invention is directed to an archival data storage system. The archival data storage system includes write once and read many (WORM) capability, data redundancy, error correction, and access control. The combination of these capabilities enable the archival storage system to be secure, error proof, and reliable. Additionally, to provide fast data access time, solid state storage devices are used in place of conventional tape drive. Solid state storage devices such as, for example, flash memory devices are fast, versatile and reliable.

TECHNICAL FIELD

The present invention relates to a data storage system and moreparticularly, some embodiments relate to a redundant data storage systemwith built in error correction and write restriction.

DESCRIPTION OF THE RELATED ART

Vast amounts of electronic data are stored, communicated, andmanipulated by modern computer systems. Some of those data need to bearchived and stored for an extended period of time. Conventionallong-term archival system uses tape storage devices or other form ofmagnetic storage devices such as magnetic disk drive.

Data stored on magnetic medium such as tape and/or disk drives canbecome corrupted over time. When this happens, it is difficult or evenimpossible to reconstruct lost data in a conventional archival system.Additionally, data can become corrupted because the medium itself ischanging with time. In conventional archival system, there is no meansto detect data corruption and a degraded storage medium. Accordingly,there is a desire for an archival system that addresses one or more ofthe above identified problems.

BRIEF SUMMARY OF EMBODIMENTS OF THE INVENTION

The present invention relates to data storage and more particularly,some embodiments relate to a redundant data storage system. In oneembodiment, the data storage system includes: an interface configured tocommunicate with an external device; a plurality of storage devicescoupled to the interface; a write once read many (WORM) moduleconfigured to allow data to be written into one or more of the pluralityof storage devices by an external device while prohibiting the externaldevice from altering the previously written data; an error correctionmodule configured to generate error correction code for data receivedfrom the external device, wherein the error correction code is storedalong with the received data and is used to correct the data if the datais corrupted upon retrieving the data; and a RAID controller configuredto generate and distribute parity data in one or more of the pluralityof storage devices.

In another embodiment, the data storage system includes a datacompression module configured to compress data received from theexternal device prior to storing the received data. The data storagesystem may include a security module configured to restrict access todata stored in the plurality of storage devices and may also include aRAID controller. The RAID controller can be configured to implementvarious RAID mode such as, for example, RAID 3 or RAID 5.

In still another embodiment, the plurality of storage devices compriseflash memory devices, and the interface may comprise a USB interface, anEthernet interface, a FC interface, a SCSI interface, or a wirelessinterface. The interface can also be wireless. The plurality of storagedevices may also comprise eight storage devices.

In still another embodiment, the data storage device includes aplurality of status indicators configured to display an operating statusof one or more of the plurality of storage devices. The data storagedevice may also include a data maintenance module configured toreconstruct any lost or corrupted data on any of the plurality ofstorage devices.

Other features and aspects of the invention will become apparent fromthe following detailed description, taken in conjunction with theaccompanying drawings, which illustrate, by way of example, the featuresin accordance with embodiments of the invention. The summary is notintended to limit the scope of the invention, which is defined solely bythe claims attached hereto.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention, in accordance with one or more variousembodiments, is described in detail with reference to the followingfigures. The drawings are provided for purposes of illustration only andmerely depict typical or example embodiments of the invention. Thesedrawings are provided to facilitate the reader's understanding of theinvention and shall not be considered limiting of the breadth, scope, orapplicability of the invention. It should be noted that for clarity andease of illustration these drawings are not necessarily made to scale.

Some of the figures included herein illustrate various embodiments ofthe invention from different viewing angles. Although the accompanyingdescriptive text may refer to such views as “top,” “bottom” or “side”views, such references are merely descriptive and do not imply orrequire that the invention be implemented or used in a particularspatial orientation unless explicitly stated otherwise.

FIG. 1 illustrates an example environment in which the invention can beimplemented according to one embodiment of the present invention.

FIG. 2 illustrates an example storage module according to one embodimentof the present invention.

FIGS. 3A-C illustrate various views of the storage module shown in FIG.2 according to one embodiment of the present invention.

The figures are not intended to be exhaustive or to limit the inventionto the precise form disclosed. It should be understood that theinvention can be practiced with modification and alteration, and thatthe invention be limited only by the claims and the equivalents thereof.

DETAILED DESCRIPTION OF THE EMBODIMENTS OF THE INVENTION

The present invention is directed toward an archival data storage systemwith write once and read many (WORM) capability, data redundancy, errorcorrection, and access control.

Before describing the invention in detail, it is useful to describe anexample environment with which the invention can be implemented. FIG. 1illustrates a data storage system 100 with which the present inventioncan be implemented. System 100 in the illustrated example includescomputing devices 105 a-b, a network 110, a server 115, an array ofstorage disk 120, and a storage area network 130. Computing devices 105a-b can any of a variety of computing devices including, for example,laptops, desktops, workstations, personal digital assistants (PDAs),handheld computing devices, or other types of computing devices in allclasses of storage from low end through enterprise class devices.

Network 110 can be implemented using any of a variety of networkarchitectures or topologies. Such networks might include, for example,the internet, a local area network (LAN), a wide area network (WAN), aplain old telephone system (POTS), or any other suitable network orcommunications channel. As shown, computing devices 105 a-b and server115 are connected to network 110. The connection to network 110 can bewireless or through a wired connection.

Server 115 can be any server system such as, for example, a conventionalstandalone file server configured to provide data services to a clientdevice such as device 105 a. Server 115 can be scalable to increasestorage capacity such as, for example, by adding storage disk array 120.Disk array 120 can be implemented as, for example, a direct-attachedstorage (DAS system). In the example architecture illustrated in FIG. 1,system 100 includes SAN 130, which includes switch 135, disk array 140,router 145, and a tape server 150. Server 115, disk array 120, and SAN130 can be implemented using one or more types of storage architecturessuch as, for example, small computer system interface (SCSI), serialadvanced technology attachment (SATA), serial attached SCSI (SAS), orfiber channel (FC). Configurations can be expanded to include mainframe,enterprise class devices as well.

Generally, a legacy SCSI system with an 8-bit wide bus can typicallydeliver data at a rate of approximately 40 megabytes per second (MBps),whereas contemporary 16-bit wide bus SCSI systems can deliver data up to320 MBps. Typical SATA systems are generally less expensive than anequivalent SCSI system and can provide performance close to that of the16-bit wide bus SCSI system at 300 MBps.

FC systems are common and more widely used than SATA and SCSI systems.FC systems offer several advantages such as pooled resources, flexiblebackup capability, scalability, fast data transfer (up to 800 MBpsfull-duplex 4 Gbit link), and the ability to accommodate long cablelengths. FC systems may have cable lengths up to 10 kilometers ascompared to a maximum cable length of 25 meters for other system suchas, for example, a SCSI system.

With continued reference to FIG. 1, the illustrated exemplary system 100can provide data access and storage redundancy by storing data atmultiple locations such as server 115, disk arrays 120 and 140, or tapeserver 150. Server 115 can be groups of remote servers, each group maybe locally or remotely connected with other groups via a network similarto network 110. As shown in FIG. 1, server 115 may access data or backupdata to disk array 140 or tape server 150 through network 110 or via adirect connection to switch 135. In this way, server 115 has theflexibility of accessing array 140 or tape server 150 via multipleconnections and thereby avoids network bottlenecks.

In one embodiment, switch 135 is an FC data switch and tape server 150is SCSI type server. In this embodiment, router 145 is configured totransfer data between a FC data bus of FC switch 135 and a SCSI bus ofSCSI tape server 150. Although a specific architecture is describedabove, components of SAN 130 may have a different architecture orcombination of architectures such as, for example, SATA, SAS, and FC.

In system 100, data redundancy can be implemented in SAN 130 byimplementing RAD across disk array 140. Parity data required forreconstructing a failed data sector can be distributed by a RAIDcontroller (not shown) located in SAN 130, across array 140, orseparately to tape server 150, or across both array 140 and tape server150. In this setup, clients 105 a-b typically can not access data storedwithin SAN 130 network when a critical component (e.g., motherboard,switch 135, power supply, etc.) of node 130 fails.

From time to time, the present invention is described herein in terms ofthis example environment. Description in terms of this environment isprovided to allow the various features and embodiments of the inventionto be portrayed in the context of an exemplary application. Afterreading this description, it will become apparent to one of ordinaryskill in the art how the invention can be implemented in different andalternative environments.

FIG. 2 illustrates a storage module 200 according to one embodiment ofthe present invention. In an example application, storage module 200 maybe implemented in tape server 150 to store data. Referring now to FIG.2, storage module 200 includes a motherboard 210, an input/output (I/O)interface 220, a plurality of storage devices 230 a-230 h, and pluralityof indicators 235. In the example shown in FIG. 2, motherboard 200includes a write once read many (WORM) engine 212, a diagnostic anderror recovery module 214, a redundant array of independent disks (RAID)controller 216, a data compression module 218, and an encryption engineand key management module 219.

I/O interface 220 comprises one or more interfaces such as, for example,universal serial bus (USB), SCSI, FC, Ethernet, parallel interface,wireless, and other suitable interface. In one embodiment, I/O interface220 comprises a USB port, an Ethernet interface, and an FC interface.The Ethernet interface may include a wire interface such as a RJ-45interface or a wireless interface that implements a wirelesscommunication standard such as IEEE 802.xx, HomeRF, or other suitablewireless standard.

WORM engine 212 allows external devices access to data stored in storagedevices 230 a-h via I/O interface 220. In one embodiment, WORM engine212 is configured to allow an external device to write a particular dataset to the storage modules only once. WORM engine 212 prohibits datarewriting to prevent data tampering of data already stored in memorydevices 230. This may be done using electronic keys or other means. Anexample of a WORM medium is CD-ROM, DVD-R, programmable read-only memory(PROM), field programmable read-only memory (FPROM). These mediums areWORM mediums as they only allow a user to write data but not to rewritedata that have already been written on the medium. Memory devices 230may comprise one or more of these WORM mediums. In one embodiment,memory devices 230 comprise re-writeable memory devices such as, forexample, a magnetic disk drive, an erasable programmable read-onlymemory (EPROM), an electrically erasable programmable read-only memory(EEPROM), a NOR-type flash memory, and a NAND-type flash memory. In thisembodiment, the WORM functionality can be implemented using electronickeys or other data write restriction method. In this way, re-writeablememory devices can be implemented as WORM devices.

Generally, in a magnetic disk, data may be erased or re-written bychanging or rewriting the magnetic signature on the magnetic medium. Inan EPROM, data may be erased by exposing the EPROM to ultraviolet (UV)light. This type of EPROM typically has a transparent window on top toallow UV light to pass. An EPROM is not considered to be a flash memorysince its data cannot be erased electronically. However, data of anEEPROM or a flash memory can be erased electrically using an electricfield. The term flash memory, as used herein, refers to various types ofnon-volatile memory that can be erased electronically such as, forexample, an EEPROM, a NOR-type flash memory and a NAND-type flashmemory. Memory devices 230 may comprise one or both the NOR-type andNAND-type flash memory devices.

In one embodiment, memory devices 230 comprise flash memory devices suchas an EEPROM memory devices. Flash memory devices have fast data accesstime. Unlike a magnetic disk drive, flash memory devices do not requirestartup time to get the disk to spin at a certain speed. Additionally,flash memory devices are versatile because they have no movingmechanical components such as the mechanical arm that supports the readhead in a magnetic drive motors and so on. As such, flash memory deviceshave very fast data read and write time as compared to a magnetic diskdrive.

As mentioned, storage module 200 also includes diagnostic and errorrecovery module 214. In one embodiment, module 214 is configured toperform error code correction (ECC) on data being read from memorydevices 230 during a read operation. Module 214 is also configured togenerate ECC codes for incoming data blocks and to append the generatedECC codes onto the end of the incoming data blocks. During a readoperation of a data block, module 214 checks the data stored in the bodyof the data block against the ECC code stored at the end of the datablock. From this comparison, module 214 may determine whether there isan error in the data block and to correct the data if an error is found.Although ECC is described, other error detection and correction methodcould also be employed by recovery module 214 such as, for example,forward error correction (FEC).

RAID controller 216 is configured to implement RAID across storagedevices 230. In this way, data redundancy is achieved. In oneembodiment, RAID controller 216 is configured to implement RAID 5 acrossstorage devices 230. In a RAID 5 system, parity data is generated andstored across storage devices 230. In this way, each storage unit ofstorage devices 230 a-g contains parity data used to reconstruct damagedor lost data where necessary. Alternatively, RAID controller 216 can beconfigured to implement RAID 3. In a RAID 3 system, parity data for allof the data stored in storage devices 230 a-h are stored on a singlestorage unit, which can be one of the storage devices 230 a-h.Implementation of RAID 3 and 5 are for illustrative purposes only. Itshould be apparent to one skilled in the art that various RAIDconfigurations (e.g. RAID 2 and RAID 10) can be implemented by RAIDcontroller 216.

In motherboard 210, data compression module 218 is configured tocompress incoming data prior to storing the incoming data in storagedevices 230. Data compression module 218 can be configured to compressincoming data using software means, hardware means, or a combination ofboth. Various data compression algorithms can be implemented bycompression module 218 such as, for example, linear predictive coding,entropy coding, Burrows-Wheeler transform, discrete cosine transform, orother suitable data compression techniques.

Encryption engine and key management module 219 is configured torestrict access to storage module 200. Before data can be write to orread from memory devices 230, the client system or user has to firstauthenticate itself to module 219. In this way, data stored in storagemodule 230 may remain secured.

As shown in FIG. 2, storage module 200 includes eight data storagedevices 230 a-h and eight status indicators 235 a-h. Each statusindicator is configured to display the operating status of an associatedstorage device. Although storage module 200 is shown to have eightstorage devices and status indicators, a different amount of storagedevices and indicators could be implemented. In one embodiment, statusindicator is configured to turn red or blink or provide some indicationwhenever its associated storage device should to be replaced. Whenever astorage device is out of service and should to be replaced, a datareconstruction and migration (data maintenance) module 255 may work withRAID controller 216 to reconstruct data stored in the out of servicestorage device. Alternatively, RAID controller 216 can be configured toperform this task alone. Once the out of service storage device isreplaced, RAID controller 216 or data maintenance module can migratedata and RAID parity data back to the newly replaced disk.

FIG. 3A illustrates an example structural design of storage module 200according to one embodiment of the present invention. FIG. 3A is anisometric view from a front angle of storage module 200. Referring nowto FIG. 3A, storage module 200 includes storage device rack areas 305 aand 305 b and guide 310. Each of the rack areas includes guide rails 310to help guide the installation of a storage device. The physicaldimensions of storage module 200 and rack areas 305 a-b are chosen suchthe storage device can be easily installed by a human user or a roboticarm. Further, the physical dimension of storage module 200 isapproximately the same as a standard tape cartridge. In this way,storage module 200 can be used with current automated archival system.

Guide 313 is configured to prevent improper installation of storagemodule 200. Guide 313 prevents an upside down installation of storagemodule 200 into a rack of a server or an archival system. Additionally,guide 313 may serve as a locking device to hold storage module 200 inplace once it is installed into a server or an archival system.

FIG. 3B illustrates an example structural design of storage module 200according to one embodiment of the present invention. FIG. 3B is anisometric view from a rear angle of storage module 200. Referring now toFIG. 3B, storage module 200 includes a guiding slot 315 and mating hole320. Slot 315 and hole 320 are used to ensure that storage module 200properly matches with a backplane (not shown) or interface of a rack ofa server or an archival system. Once storage module 200 is properlyinstalled, interface 220 will be able to communicate with the hostserver or archival system. As shown in FIG. 3B, interface 220 comprisesa parallel interface. It should be noted that other type of interfacescould be used such as, for example, USB, SCSI, FC, and Ethernet. FIG. 3Cillustrate a top view of storage module 200.

Unless defined otherwise, all technical and scientific terms used hereinhave the same meaning as is commonly understood by one of ordinary skillin the art to which this invention belongs. All patents, applications,published applications and other publications referred to herein areincorporated by reference in their entirety. If a definition set forthin this section is contrary to or otherwise inconsistent with adefinition set forth in applications, published applications and otherpublications that are herein incorporated by reference, the definitionset forth in this section prevails over the definition that isincorporated herein by reference.

The term tool can be used to refer to any apparatus configured toperform a recited function. For example, tools can include a collectionof one or more modules and can also be comprised of hardware, softwareor a combination thereof. Thus, for example, a tool can be a collectionof one or more software modules, hardware modules, software/hardwaremodules or any combination or permutation thereof. As another example, atool can be a computing device or other appliance on which software runsor in which hardware is implemented.

As used herein, the term module might describe a given unit offunctionality that can be performed in accordance with one or moreembodiments of the present invention. As used herein, a module might beimplemented utilizing any form of hardware, software, or a combinationthereof. For example, one or more processors, controllers, ASICs, PLAs,logical components, software routines or other mechanisms might beimplemented to make up a module. In implementation, the various modulesdescribed herein might be implemented as discrete modules or thefunctions and features described can be shared in part or in total amongone or more modules. In other words, as would be apparent to one ofordinary skill in the art after reading this description, the variousfeatures and functionality described herein may be implemented in anygiven application and can be implemented in one or more separate orshared modules in various combinations and permutations. Even thoughvarious features or elements of functionality may be individuallydescribed or claimed as separate modules, one of ordinary skill in theart will understand that these features and functionality can be sharedamong one or more common software and hardware elements, and suchdescription shall not require or imply that separate hardware orsoftware components are used to implement such features orfunctionality.

While various embodiments of the present invention have been describedabove, it should be understood that they have been presented by way ofexample only, and not of limitation. Likewise, the various diagrams maydepict an example architectural or other configuration for theinvention, which is done to aid in understanding the features andfunctionality that can be included in the invention. The invention isnot restricted to the illustrated example architectures orconfigurations, but the desired features can be implemented using avariety of alternative architectures and configurations. Indeed, it willbe apparent to one of skill in the art how alternative functional,logical or physical partitioning and configurations can be implementedto implement the desired features of the present invention. Also, amultitude of different constituent module names other than thosedepicted herein can be applied to the various partitions. Additionally,with regard to flow diagrams, operational descriptions and methodclaims, the order in which the steps are presented herein shall notmandate that various embodiments be implemented to perform the recitedfunctionality in the same order unless the context dictates otherwise.

Although the invention is described above in terms of various exemplaryembodiments and implementations, it should be understood that thevarious features, aspects and functionality described in one or more ofthe individual embodiments are not limited in their applicability to theparticular embodiment with which they are described, but instead can beapplied, alone or in various combinations, to one or more of the otherembodiments of the invention, whether or not such embodiments aredescribed and whether or not such features are presented as being a partof a described embodiment. Thus, the breadth and scope of the presentinvention should not be limited by any of the above-described exemplaryembodiments.

Terms and phrases used in this document, and variations thereof, unlessotherwise expressly stated, should be construed as open ended as opposedto limiting. As examples of the foregoing: the term “including” shouldbe read as meaning “including, without limitation” or the like; the term“example” is used to provide exemplary instances of the item indiscussion, not an exhaustive or limiting list thereof; the terms “a” or“an” should be read as meaning “at least one,” “one or more” or thelike; and adjectives such as “conventional,” “traditional,” “normal,”“standard,” “known” and terms of similar meaning should not be construedas limiting the item described to a given time period or to an itemavailable as of a given time, but instead should be read to encompassconventional, traditional, normal, or standard technologies that may beavailable or known now or at any time in the future. Likewise, wherethis document refers to technologies that would be apparent or known toone of ordinary skill in the art, such technologies encompass thoseapparent or known to the skilled artisan now or at any time in thefuture.

A group of items linked with the conjunction “and” should not be read asrequiring that each and every one of those items be present in thegrouping, but rather should be read as “and/or” unless expressly statedotherwise. Similarly, a group of items linked with the conjunction “or”should not be read as requiring mutual exclusivity among that group, butrather should also be read as “and/or” unless expressly statedotherwise. Furthermore, although items, elements or components of theinvention may be described or claimed in the singular, the plural iscontemplated to be within the scope thereof unless limitation to thesingular is explicitly stated.

The presence of broadening words and phrases such as “one or more,” “atleast,” “but not limited to” or other like phrases in some instancesshall not be read to mean that the narrower case is intended or requiredin instances where such broadening phrases may be absent. The use of theterm “module” does not imply that the components or functionalitydescribed or claimed as part of the module are all configured in acommon package. Indeed, any or all of the various components of amodule, whether control logic or other components, can be combined in asingle package or separately maintained and can further be distributedin multiple groupings or packages or across multiple locations.

Additionally, the various embodiments set forth herein are described interms of exemplary block diagrams, flow charts and other illustrations.As will become apparent to one of ordinary skill in the art afterreading this document, the illustrated embodiments and their variousalternatives can be implemented without confinement to the illustratedexamples. For example, block diagrams and their accompanying descriptionshould not be construed as mandating a particular architecture orconfiguration.

1-20. (canceled)
 21. A data storage device, comprising: an interfaceconfigured to communicate with an external device; a plurality ofstorage devices coupled to the interface; a write once read many (WORM)module configured to allow data to be written into one or more of theplurality of storage devices by an external device while prohibiting theexternal device from altering the previously written data; an errorcorrection module configured to generate error correction code for datareceived from the external device, wherein the error correction code isstored along with the received data and is used to correct the data ifthe data is corrupted upon retrieving the data; a RAID controllerconfigured to generate and distribute parity data in one or more of theplurality of storage devices; a data compression module configured tocompress data received from the external device prior to storing thereceived data; and an encryption and key management module configured torestrict access to data stored in the plurality of storage devices. 22.The data storage device of claim 21, wherein the RAID controller isoperative to distribute the parity data across a plurality of thestorage devices.
 23. The data storage device of claim 21, wherein theplurality of storage devices comprise flash memory devices.
 24. The datastorage device of claim 21, wherein the interface comprises a USBinterface, an Ethernet interface, a FC interface, a SCSI interface, or awireless interface.
 25. The data storage device of claim 21, wherein theinterface is wireless.
 26. The data storage device of claim 21, whereinthe plurality of storage devices comprise eight storage devices.
 27. Thedata storage device of claim 21, further comprising a plurality ofstatus indicators configured to display an operating status of one ormore of the plurality of storage devices.
 28. The data storage device ofclaim 21, further comprising a data maintenance module configured toreconstruct any lost or corrupted data on any of the plurality ofstorage devices.
 29. The data storage device of claim 21 wherein theencryption and key management module is configured to authenticate anexternal device or user before allowing read or write access to theplurality of storage devices.
 30. A data storage device, comprising: aninterface configured to communicate with one or more client devices; aplurality of flash memory storage devices coupled to the interface; awrite once read many (WORM) module configured to allow data to bewritten into one or more of the plurality of flash memory storagedevices by a client device while restricting the client device fromaltering the previously written data; an error correction moduleconfigured to generate error correction code for data received from theclient device, wherein the error correction code is stored along withthe received data and is used to correct the data if the data isdetermined to be corrupted; a RAID controller configured to generate anddistribute parity data in one or more of the plurality of storagedevices; a data compression module configured to compress data receivedfrom the client device prior to storing the received data; and asecurity module configured to restrict access to data stored in theplurality of storage devices.
 31. The data storage device of claim 30,wherein the WORM module is configured to use electronic keys to restrictthe client device from altering the previously written data.
 32. Thedata storage device of claim 30, wherein the RAID controller isoperative to distribute the parity data across a plurality of thestorage devices.
 33. The data storage device of claim 30, wherein theinterface comprises a USB interface, an Ethernet interface, a FCinterface, a SCSI interface, or a wireless interface.
 34. The datastorage device of claim 30, wherein the interface is wireless.
 35. Thedata storage device of claim 30, wherein the plurality of flash memorystorage devices comprise eight flash memory storage devices.
 36. Thedata storage device of claim 30, further comprising a plurality ofstatus indicators configured to display an operating status of one ormore of the plurality of flash memory storage devices.
 37. The datastorage device of claim 30, further comprising a data maintenance moduleconfigured to reconstruct any lost or corrupted data on any of theplurality of flash memory storage devices.
 38. The data storage deviceof claim 21, wherein the security module is configured to authenticateclient device or user before allowing read or write access to theplurality of flash memory storage devices.
 39. A data storage device,comprising: a plurality of flash memory devices; a write once read many(WORM) module configured to allow data to be written into one or more ofthe plurality of flash memory devices by an external device whileprohibiting the external device from altering the previously writtendata; a RAID controller configured to generate and distribute paritydata in one or more of the plurality of flash memory devices; a datamaintenance module configured to reconstruct any lost or corrupted dataon any of the plurality of flash memory devices; a data compressionmodule configured to compress data received from the external deviceprior to storing the received data; and an encryption and key managementmodule configured to authenticate an external device or user beforeallowing read or write access to the plurality of flash memory devices.40. The data storage device of claim 39, further comprising an errorcorrection module configured to generate error correction code for datareceived from the external device, wherein the error correction code isstored along with the received data and is used to correct the data ifthe data is corrupted.